1. Field of the Invention
The present invention relates to an electric fan used for moving air to a radiator of a vehicle. More particularly, the present invention relates to a structure for introducing cooling air into a motor for driving a fan.
2. Description of the Related Art
Concerning the device for introducing cooling air into a motor of an electric fan for vehicle use, the device described in the official gazette of JP-A-9-74718 is well-known.
According to the above patent document, cooling air introducing port, which is directed downward, is formed in an end portion of an end housing of a motor used for driving a fan. Further, first to the third labyrinth plates are provided in a passage from this cooling air introducing port to the inside of the motor.
The first labyrinth plate is contacted with and fixed to a cylindrical main body housing of the motor and directed in the direction substantially perpendicular to the horizontal direction when the motor is mounted on a vehicle. The second labyrinth plate is contacted with and fixed to the cylindrical main body housing on the inner side of the motor compared with the first labyrinth plate and extended in the substantially same direction as that of the first labyrinth plate. The third labyrinth plate is extended in the horizontal direction from the end housing to the inside of the motor.
According to the structure described in the above patent document, the labyrinth structure including the first to the third labyrinth plate is composed in a relatively short range in the neighborhood of the cooling air introducing port in the cylindrical main body housing of the motor. Therefore, water and dust flowing into the device together with cooling air cannot be sufficiently separated.
Therefore, in order to sufficiently separate water and dust from the cooling air, it is necessary to design a sectional area of a passage in the labyrinth structure to be small. As a result, the following problems may be encountered. The ventilating resistance of the labyrinth structure is increased, and a volume of the cooling air is decreased. Accordingly, the motor cooling performance is lowered.